Band-saw mill.



F. L. WALKER & we. DIITBENNER.

BAND SAW MILL.

APPLICATION FILED MAR. 17. I916- 1. 259 559, Patented Mar. 19, 1918. E 2 SHEETS-SHEET F. L. WALKER & H. G. DITTBENNER.

BAND SAW MILL.

APPLICATION FILED MAR.17,1916. 1 359,569. Patented Mar. 19% was.

. 2 SHEETr-SHEET 3.

FLETCHER L. WALKER AND HEBMANN G. DITTBENNER, F MINNEAPOLIS, MINNESOTA.

BAND-SAW MILL.

Specification of Letters Patent.

Patented Mar. 19, 1918.

Application filed March 17, 1916. Serial No. 84,766.

To all whom it may concern:

Be it known that we, FLETCHER L. WALKER and HERMANN G. DITTBENNER, citizens of the United States, residing at Minneapolis, in the county of Hennepin and State of Minnesota, have invented certain new and useful Improvements in Band-Saw Mills; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Our invention relates to band saw mills and has for its object to provide an improved saw tension mechanism or device therefor, and to such ends, generally stated, the invention consists of the novel devices and combinations of devices hereinafter described and defined in the claims.

In the accompanying drawings which illustrate the invention, like characters indicate like parts throughout the several views.

Referring to the drawings:

Figure 1 is a plan view illustrating the invention as incorporated in a band saw mill; 7

Fig. 2 is a side elevation of the machine shown in Fig. 1, some parts being broken away and some parts being sectioned;

Fig. 3 is a detail in side elevation with parts broken away, showing the fulcrum and intermediate portion of the so-called extension yoke;

Fig. 4: is a detail in rear elevation showing one of the pedestal links;

Fig. 5 is a detail in plan showing a portion of a ratchet wheel and cooperating dogs; and V 40 Fig. 6 is a rear elevation of the ratchet dogs removed from the operating lever.

Of the parts of the band saw mill, the numeral 1 indicates the bed frame having laterally spaced vertical pedestals 1 The numeral 2 indicates the sliding columns which are mounted for vertical movements in the frame pedestals 1 The numerals 3 and 4 indicate, respectively, the lower and upper band saw wheels, the former of which is journaled in suitable bearings on the bed frame 1', and the latter of which are journaled in suitable hearings on the sliding columns 2. The saw, which runs over the wheels 3 and 4c, is indicated by the numeral 5. I

The parts above described are of Well known band saw mill construction. The log carriage which cooperates with the saw is not illustrated, but its construction and arrangement is well known.

By reference to Fig. 2, it will be noted that the pedestals 2 are notched or cut back at 6, between the upper and lower saw wheels 3 and 4:, to points back of a vertical line intersecting the axes of the said wheels. This gives clearance for very wide boards. The so-called haul-off rollers 7, as shown, are of the novel construction and arrangement disclosed and claimed in our co-pending application, Serial Number 71,207 filed of date January 10, 1916, and entitled Band saw mill, and their shafts 8 are journaled in suitable bearings on the bed frame 1. They, of course, receive the boards sawed from the log and feed the same endwise from the band saw mill. The purpose of their spiral blades and other novel features need not be herein discussed since they are fully disclosed andclaimed in our said earlier application. I

In the operation of band saw mills, it has hitherto been the common practice to put the saws under the tension of approximately 10,000 pounds, but we have found in actual practice that by putting the band saws under a tension of from 40,000 to 50,000 pounds, not only can the sawing action be greatly improved, but that the wear and tear on the band saws can be decreased and the life of the saws increased. For example, in practice, in a band saw mill with the band saw under a tension of 10,000 pounds, it was only possible to saw nine inches for each complete revolution of a forty-four foot saw. We substituted a two-gage thinner saw of even shorter length, put the same under a tension of 45,000 pounds and produced a twentyseven inch cut of equal depth for each complete revolution of the saw.

Under this veryhigh tension, the saw cannot be forced off from the band saw wheels and the vibration of the saw, as well as the liability thereof to twist under high sawing pressure, 'is very greatly reduced. As a consequence of the reduced vibration of the saw, the tendency of the saw to crystallize is reduced, and crystallization, as is well known, is one of the main causes of saw breakage.

For thus putting the band saw under the abovenoted high tension, we provide a saw tensi n eviceof, n vel o s ruction and a rangement. The sliding columns 2 are ca.-

p able of independent vertical movements,

and the journals between the saw wheel shafts and these columns, as is customary, will permit suflicient variation in the vertical movements of. the columns to provide for tilting of the upper saw wheel slightly, and thereby adjusting the same to the two slightly varying difierences in the length of thetoothed edge and back edgeof the band saw. Thelower portions at least of said columns 2 are tubular and terminate in in terior fiat bearing surfaces at 9 (see Fig. 2). These flat bearing surfaces are engaged by the rounded upper ends oflinks 10 that are placed within the tubular lower portions of; the columns, fastened to the said columnsby. transverse bolts 11 passed through the said links and columns below the rounded upper ends of the former. The bolt holes in the links 10, however, are considerably larger than the bolts 11, so that the bearing contact may always be'between the rounded upper ends of thelinks and the'fi-at bearing surfaces 9 of the columns. The lower ends of the links 10 are bifurcated (see Fig. 4) and extended therethrough, are small knife-edge bars 12, that rest in flaring seats 13 formed in the extended laterally spaced arms 1 1 of a so cal-led tension yoke made up of the said arms, and a heavy connecting shaft 15, and a third extended arm 16. The said elements 14, 15 and 16 are preferably cast integral and are made very heavy and strong, so that there will be no perceptible bend or detrimental spring therein. Beyond the ends of the connecting shaft 15 proper, the rear ends of the arms 14 are provided with seats that receive and adj-'ustably hold knife edged fulcrum blocks 17 that rest upon the flaring seats formed in the upper ends of heavy bearingjlugs 18, which, as shown, are cast integral with the bases of the pedestalsl The fulcrum blocks or members 17 are made independently adjustable, by screw rods 19 that have screw-threaded engagement with the rear end portions of the 'saidarms 1%.

Hence, by independent adjustments of the two screws 19 andv fulcrum blocks 17, the entire tension yoke may be tilted so as to move the one or the other of-thef columns 2 I higherthan the other, and thus tilt or cant the upper saw wheel so that it will properly engage the bandsaw. Once the proper tilt is given to the saw wheel, such ti-lt will be maintained and the tension will be transmitted to the saw equally through the two columns.

Here it should be noted that the rear end of the heavy outwar'dly'extended arm 16 terminates at a point that is in line with the transverse center of the saw, and which line is midway between the az'iiso'f the two columns? This is inap6r'ta1it"'be use it to the two columns;

and at their upper ends, are

causes the downward pressure on the rear end of said arms 16 to be. delivered equally To the rear end'of the said arms 16 is attached a cable in the form ofa chain 20, the lower end of which is attached to and wound upon a Windlass shaft 21 journaled in a heavy bearing brackets 22 rigidly bolted to the mill base 1. R-igidly secured heavy ratchet wheel 23 formed, as shown, with a peripheral groove in whichthe upper end of a cable a twisted wire cable is anchored; To the lower end of this cable 24: is attached a weight 25, which, acting through the connections described, is just about sufficient to OOlllltGlPOlSGtl-le weight of the columns 2 and theupper saw wheel.

The numeral 26 indicates a long heavy tension lever, the inner end of which, as shown, is bifurcated so that it straddles the ratchet wheel: 22 and is pivoted'loosely on the windl-ass shaft 21. By means of a pin or bolt 27 a three-part ratchet dog 28 2929 is pivoted to the lever 26 for cocpera; tion with the teeth of theratchet wheel 23. Here it shouldbe noted that the teeth of the said ratchet wheel arerectangular so that the wheel is capable of being driven in either direction. lVhen the upper dog 28 thrown outward, its shoulder 28 will engage the dogs 29 and will then serve to hold by gravity the said dogs 29 for action on the teeth ofthe ratchet wheel 23, so that they will then support the tension lever 26 in an extended position, as shown in Figs. 1 and 2. A heavy weight 30 applied on the outer end of the lever 26 operates through the connectionsdescribed to put the saw under the high tension above noted! This weight 80 willbe very heavy, and consequently, a block and tackle (not shown) will usually be'applied for the purpose of applying the weight to the lever 26 or for removing it'therefrom. When the weight 30 is removed from the lever 26, the tension will be removed from the "saw, but the upper saw wheel, being approximately v counter-balanced by the weight 25, willnot drop downward and release it selffrom the saw. To produce the, release of'the upper wheel from the saw, so that the saw may be appliedor removed, the dog 28 is turned over'or upside down, andthedogs 29 will then drop down into inoperative positions and thenthe, lever 26 be used by upward movement,to positively. release the weight 25, and thereby permit the upper saw wheel to drop and, give sla ck;to"th saw.

' Itis also important to note thatthe shaftforming portion of the tensionyoke islecated in the space surrounded by the saw 24: shown as in the form of to the windlass shaft 21 is a said tension Yoke extends p side; of

the saws-what the hand} saw'inay he applied and removed without disturbing the said socalled tension yoke. The term tension yoke is used inthe broad and liberal sense.

What we claim is:

1. In the band saw mill, the combination with upper and lower saw wheels and vertically sliding columns supporting said upper wheel, of a rigidly formed tension yoke comprising a transverse shaft, a pair of forwardly projecting arms and a rearwardly projecting arm, the latter extending from one end of the shaft and terminating on a line midway between the two forwardly projecting arms, said sliding columns being supported one from each of the forwardly pro ecting arms, fulcrums on which the ends of the shaft are mounted, and means applied to the end of the rearwardly projecting arm for rocking the yoke on its trunnions to raise the columns and thereby place the saw under tension.

2. In a band saw mill, the combination with upper and lower saw wheels and verticallysliding columns supporting said upper wheel, of a rigidly formed tension yoke comprising a transverse shaft, a pair of forwardly projecting arms and a rearwardly projecting arm, the latter extending from one end of the shaft and terminating on a line midway between the two forwardly projecting arms, said sliding columns being supported one from each of the forwardly projecting arms, fulcrums on which the ends of the shaft are mounted,

and means applied to the end of the rearwardly projecting arm for rocking the yoke on its trunnions to raise the columns and thereby place the saw under tension, said fulcrums comprising relatively fixed bearing lugs and vertically adjustable blocks carried by the yoke and engaging the bearing lugs.

3. In a band saw mill, the combination with upper and lower band saw wheels and vertically sliding columns supporting said upper wheel, of an intermediately fulcrumed tension yoke having laterally spaced forwardly projected arms that support the said columns and having a rearwardly projecting arm, a Windlass shaft connected to the rearwardly projecting arms of said yoke, a bifurcated ratchet wheel secured to said Windlass shaft and having a sheave surface between its two rows of ratchet teeth, a weighted cable attached to the sheave surface of said ratchet wheel, a lever pivoted around the axis of said Windlass shaft, and provided with two gravity-actuated ratchet dogs and a weighted upwardly projecting ratchet dog, which latter, when operative, releases said depending ratchet dogs, but when released, throws the said depending ratchet dogs into action, and means applied to said tension lever for putting the saw under tension.

In testimony whereof I aliix my signature in presence of witnesses.

FLETCHER L. WALKER.

W'itnesses:

R. F. PRAY, GILBEN M. WALKER, LUCILLE M. Dow.

In testimony whereof I aflix my signature in presence of two witnesses.

HERMANN G. DITTBENNER.

Witnesses:

HARRY D. KILGORE, F. D. MERCHANT.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

